Canadian Hackers.

I'm guessing this prank - by a bunch of techno-literate campaigners in Toronto, Canada - got plenty of people enraged, amused or just plain mystified. Would it make you leave your car at home though? The signs usually advertise events at the University of Toronto, but have started doing their bit to save the planet. A video here shows them telling passersby 'Take your SUV/back to detroit' and to 'walk, bike, TTC/ Don't drive'. For those, like me, that didn't know what TTC means, it's the authority that operates public transport in Toronto.

Personally, I'm not sure it'll work. SUV's are still getting more popular despite getting loads of stick. Although its interesting to imagine governments using billboards to display prominent 'green' messages, anti-smoking campaigns have found using scare tactics isn't straightforward.